In the course of the manufacture of many articles, including printed circuit boards, the boards, printed circuit film, or other panels are generally delivered along a preferably horizontal path, while being horizontally disposed, as they pass through a chamber in a longitudinal direction from inlet to outlet. During the course of such delivery, and particularly with respect to printed circuit boards, film and the like, it has become commonplace to etch surface portions of the panels, or boards, removing metallic material from the upper and lower surfaces thereof. Generally, such metallic material is copper, and the etchant can be any of various etchants capable of removing metallic material from surfaces of the boards.
As such boards or panels traverse an etching chamber, from inlet to outlet, it has been noticed that, because etchant is being dispersed on the boards from various spray nozzles, often with fairly uniform application of etchant, there is a tendancy for perimeter surface portions of the panels to become etched to greater depths than central surface portions of the panels. It is believed that this phenomena is due to upper and lower panel surfaces generally seeing more etchant at their perimeters than at central surface portions, as a result of flow of etchant from central surface portions outwardly over edges, such that the perimeter or edge portions of the panels receive not only the spray that is impinged directly thereon, but also etchant that was sprayed onto central surface portions of the panels and which runs across the perimeter portions of the panels, as it leaves the panels by travelling over perimeter edges.
In instances in which the depth of metal on panel surfaces is of minimal thickness, more greatly etched perimeter surface portions of the panels may result in an undesirable depth of metal being etched from the panels, leaving the metal surface portions at the perimeters of the panels too greatly etched, or having insufficient metal thereon, for proper subsequent uses, such as for proper carrying of electrical signals, or the like, especially in instances when the panels are printed circuit boards.